Question: Simplify the following expression: $r = \dfrac{8a}{4a + 4} - \dfrac{-9}{4a + 4}$
Solution: Since the expressions have the same denominator we simply subtract the numerators: $r = \dfrac{8a - (-9)}{4a + 4}$ Distribute the negative sign: $r = \dfrac{8a + 9}{4a + 4}$ Combine like terms: $r = \dfrac{8a + 9}{4a + 4}$